the most common std is Human Pappillomavirus. there are over 100 strains. it can lead to cervical cancer. most strains just cause genital warts. condoms dont protect you completley from the virus, because the entire pelvic region is infected. condoms can not prevent the transmission of hpv, though some studies suggest that they do reduce the risk of cervical cancer. there is one vaccine, Gardosil, which is now in the process of fda approval. it only protects women from cervical cancer due to hpv. 80% of all sexually active adults have had atleast one strain in thier lifetime. many never show symptoms but can still pass it on.